Effervescent atomizing structure and method of operation for rotating detonation propulsion system

ABSTRACT

A method and system of effervescent atomization of liquid fuel for a rotating detonation combustor (RDC) for a propulsion system is provided. The method includes flowing liquid fuel through a fuel injection port of a nozzle assembly of the RDC system; flowing a gas through the fuel injection port of the nozzle assembly volumetrically proportional to the liquid fuel; producing a gas-liquid fuel mixture at the fuel injection port by mixing the flow of gas and the flow of liquid fuel; flowing an oxidizer through a nozzle flowpath of the RDC system; producing an oxidizer-gas-liquid fuel mixture by mixing the gas-liquid fuel mixture and the flow of oxidizer within the nozzle flowpath; and igniting the oxidizer-gas-liquid fuel mixture within a combustion chamber of the RDC system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/618,637 “EFFERVESCENT ATOMIZING STRUCTURE AND METHOD OF OPERATION FORROTATING DETONATION PROPULSION SYSTEM”, having a filing date of Jun. 9,2017, and which is incorporated herein by reference in its entirety.

FIELD

The present subject matter relates generally to a system of continuousdetonation in a propulsion system.

BACKGROUND

Many propulsion systems, such as gas turbine engines, are based on theBrayton Cycle, where air is compressed adiabatically, heat is added atconstant pressure, the resulting hot gas is expanded in a turbine, andheat is rejected at constant pressure. The energy above that required todrive the compression system is then available for propulsion or otherwork. Such propulsion systems generally rely upon deflagrativecombustion to burn a fuel/air mixture and produce combustion gasproducts which travel at relatively slow rates and constant pressurewithin a combustion chamber. While engines based on the Brayton Cyclehave reached a high level of thermodynamic efficiency by steadyimprovements in component efficiencies and increases in pressure ratioand peak temperature, further improvements are welcomed nonetheless.

Accordingly, improvements in engine efficiency have been sought bymodifying the engine architecture such that the combustion occurs as adetonation in either a continuous or pulsed mode. The pulsed mode designinvolves one or more detonation tubes, whereas the continuous mode isbased on a geometry, typically an annulus, within which single ormultiple detonation waves spin. For both types of modes, high energyignition detonates a fuel/air mixture that transitions into a detonationwave (i.e., a fast moving shock wave closely coupled to the reactionzone). The detonation wave travels in a Mach number range greater thanthe speed of sound (e.g., Mach 4 to 8) with respect to the speed ofsound of the reactants. The products of combustion follow the detonationwave at the speed of sound relative to the detonation wave and atsignificantly elevated pressure. Such combustion products may then exitthrough a nozzle to produce thrust or rotate a turbine. With variousrotating detonation systems, the task of preventing backflow into thelower pressure regions upstream of the rotating detonation has beenaddressed by providing a steep pressure drop into the combustionchamber. However, such may reduce the efficiency benefits of therotating detonation combustion system.

Generally, a detonation combustion system is based on whether a minimumquantity of detonation cells can be sustained in an annular combustionchamber. The detonation cell is characterized by a cell width (λ) thatdepends on the type of fuel and oxidizer as well as the pressure andtemperature of the reactants at the combustion chamber and thestoichiometry (ϕ) of the reactants. For each combination of fuel andoxidizer, cell size decreases with increasing pressure and temperature,and for stoichiometry greater than or less than 1.0. In variouspropulsion system apparatuses, such as for gas turbine engines, the cellwidth may decrease by 20 times or more from a lowest steady stateoperating condition (e.g., ground idle) to a highest steady stateoperating condition (e.g., maximum takeoff).

It is generally known in the art that combustion chamber geometry isdefined by a desired detonation cell size based on the fuel-oxidizermixture and the pressure, temperature, and stoichiometric ratio thereof.Various combinations of fuel-oxidizer mixture, pressure, temperature,and stoichiometric ratio (e.g., at various operating conditions of thepropulsion system) may render a fixed geometry combustion chamberinefficient at more than one operating condition. However, variablegeometry combustion chambers generally involve complex structures thatmay significantly reduce or eliminate overall propulsion systemefficiency or operability.

Rotating detonation combustors are generally annular and requirefuel-oxidizer injection to approach pre-mixed conditions in minimallength while mitigating flameholding within the combustion combustor.Thus, rotating detonation combustion systems generally require aplurality of minimally sized orifices for rapid mixing of fuel andoxidizer within the injector. The liquid fuel also needs to be atomizedinto very small droplets for the rotating detonation wave to beaffected. Liquid fuel atomization may generally be due to momentumtransfer from the air streams of the injector.

However, such known geometries generally inhibit application of rotatingdetonation combustion systems into increasingly smaller apparatuses, orgenerally require tight-tolerance features that increase the complexityof manufacturing of the combustion system, each of which may limitapplication of rotating detonation combustion systems.

Therefore, there is a need for a detonation combustion system thatprovides improved liquid fuel atomization. Additionally, there is a needfor a detonation combustion system that provides a desired detonationcell size across a plurality of operating conditions.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

The present disclosure is directed to a method of effervescentatomization of liquid fuel for a rotating detonation combustor (RDC) fora propulsion system. The method includes flowing liquid fuel through afuel injection port of a nozzle assembly of the RDC system; flowing agas through the fuel injection port of the nozzle assemblyvolumetrically proportional to the liquid fuel; producing a gas-liquidfuel mixture at the fuel injection port by mixing the flow of gas andthe flow of liquid fuel; flowing an oxidizer through a nozzle flowpathof the RDC system; producing an oxidizer-gas-liquid fuel mixture bymixing the gas-liquid fuel mixture and the flow of oxidizer within thenozzle flowpath; and igniting the oxidizer-gas-liquid fuel mixturewithin a combustion chamber of the RDC system.

In one embodiment, producing a gas-liquid fuel mixture includesproducing a volumetric flow ratio of gas to liquid fuel of approximately1000% or less.

In another embodiment, flowing a gas includes flowing air or inert gas.

In various embodiments, flowing a gas includes flowing a gaseous fuel.In one embodiment, flowing a gaseous fuel includes flowing a gaseousfuel defining a detonation cell width of the gaseous fuel less than adetonation cell width of the liquid fuel.

In another embodiment, flowing a gas includes flowing a gas at apressure greater than the flow of liquid fuel within the fuel injectionport.

In still another embodiment, producing a gas-liquid fuel mixtureincludes producing a mass flow ratio of gas to liquid fuel ofapproximately 30% or less.

In still yet another embodiment, producing a gas-liquid fuel mixturedefines an annular flow, a mist flow, or a disperse flow of thegas-liquid fuel mixture based at least on a gas volumetric flux and aliquid fuel volumetric flux.

The present disclosure is further directed to a method of operating apropulsion system at an approximately constant detonation cell size fora propulsion system including a rotating detonation combustion (RDC)system. The method includes flowing a liquid fuel through a fuelinjection port of a nozzle assembly of the RDC system; flowing a gaseousfuel through the fuel injection port of the nozzle assemblyvolumetrically proportional to the liquid fuel; producing a gas-liquidfuel mixture at the fuel injection port by mixing the flow of gas andthe flow of liquid fuel; flowing an oxidizer through a nozzle flowpathof the RDC system; producing an oxidizer-gas-liquid fuel mixture bymixing the gas-liquid fuel mixture and the flow of oxidizer within thenozzle flowpath; igniting the oxidizer-gas-liquid fuel mixture within acombustion chamber of the RDC system; and adjusting a volumetric flow ofgaseous fuel relative to the liquid fuel based at least on a commandedoperating condition of the propulsion system.

In one embodiment, flowing a gaseous fuel is based at least on a desireddetonation cell size at a first operating condition of the propulsionsystem.

In various embodiments, adjusting the volumetric flow of gaseous fuel isbased at least on maintaining an approximately constant detonation cellwidth at a second operating condition greater than the first operatingcondition. In one embodiment, adjusting the volumetric flow of gaseousfuel is based at least on maintaining an approximately constantdetonation cell width at a stoichiometric ratio of approximately 1.0 orless at the second operating condition.

In another embodiment, adjusting the volumetric flow of gaseous fuel isbased at least on a pressure and a temperature of oxidizer at the RDCsystem.

In still another embodiment, flowing a gaseous fuel includes flowing agaseous fuel defining a detonation cell width of the gaseous fuel lessthan a detonation cell width of the liquid fuel.

In still yet another embodiment, the method further includes adjustingthe flow of liquid fuel based at least on the commanded operatingcondition of the propulsion system.

In one embodiment, producing a gas-liquid fuel mixture includesproducing a volumetric flow ratio of gas to liquid fuel of approximately1000% or less.

In another embodiment, producing a gas-liquid fuel mixture includesproducing a mass flow ratio of gas to liquid fuel of approximately 30%or less.

In still another embodiment, producing a gas-liquid fuel mixture definesan annular flow, a mist flow, or a disperse flow of the gas-liquid fuelmixture based at least on a gas volumetric flux and a liquid fuelvolumetric flux.

The present disclosure is further directed to a system for providingeffervescent atomization of a liquid fuel to a rotating detonationcombustion (RDC) system for a propulsion system. The propulsion systemincludes a first pump configured to provide variable flow rates of a gasto the RDC system and a second pump configured to provide variable flowrates of a liquid fuel to the RDC system, and a computing devicecomprising one or more processors and one or more memory devices, theone or more memory devices storing instructions that when executed bythe one or more processors cause the one or more processors to performoperations. The operations include receiving a commanded operatingcondition from a propulsion system operator, in which the commandedoperating condition is indicative of one or more parameters based atleast on one or more of a commanded thrust output, shaft speed, andengine pressure ratio, and the one or more parameters includes a liquidfuel flow rate and a pressure and temperature of oxidizer at the RDCsystem; and determining a volumetric flow rate of gas to mix with theliquid fuel based at least on the liquid fuel flow rate and a desiredtwo-phase flow regime of a gas-liquid fuel mixture.

In one embodiment of the system, determining a volumetric flow rate ofgas to mix with the liquid fuel is further based on maintaining adesired detonation cell width at a combustion chamber of the RDC system,and wherein the desired detonation cell width is based at least on apressure and temperature of oxidizer at the RDC system, a volumetricflow ratio of a mixture of a gaseous fuel and a liquid fuel, an annulargap of the combustion chamber, and a combustion chamber length.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a schematic view of a propulsion system in accordance with anexemplary embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of a rotating detonation combustionsystem in accordance with another exemplary embodiment of the presentdisclosure;

FIG. 3 is an exemplary embodiment of a combustion chamber of a rotatingdetonation combustion system in accordance with an embodiment of thepresent disclosure;

FIG. 4 is an exemplary embodiment of a portion of the propulsion systemgenerally depicting a flow of a gas-liquid fuel mixture to a rotatingdetonation combustion system;

FIG. 5 is another exemplary embodiment of a portion of the propulsionsystem generally depicting a flow of a gas-liquid fuel mixture to arotating detonation combustion system;

FIG. 6 is an exemplary embodiment of a chart generally showing two phaseflow regimes as a function of gas volumetric flux and liquid volumetricflux according to an aspect of the present disclosure;

FIG. 7 is a flowchart outlining steps of a method of providingeffervescent fuel atomization to a rotating detonation combustion systemin accordance with an embodiment of the present disclosure; and

FIG. 8 is a flowchart outlining steps of a method of operating apropulsion system at an approximately constant cell size in accordancewith an embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

The terms “forward” and “aft” refer to relative positions within apropulsion system or vehicle, and refer to the normal operationalattitude of the propulsion system or vehicle. For example, with regardto a propulsion system, forward refers to a position closer to apropulsion system inlet and aft refers to a position closer to apropulsion system nozzle or exhaust.

The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

Approximating language, as used herein throughout the specification andclaims, is applied to modify any quantitative representation that couldpermissibly vary without resulting in a change in the basic function towhich it is related. Accordingly, a value modified by a term or terms,such as “about”, “approximately”, and “substantially”, are not to belimited to the precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value, or the precision of the methods or machines forconstructing or manufacturing the components and/or systems. Forexample, the approximating language may refer to being within a 10percent margin.

Here and throughout the specification and claims, range limitations arecombined and interchanged, such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

Methods and structures for operating a propulsion system including arotating detonation combustion system are provided for improved liquidfuel atomization. The methods and structures provided herein may furtherprovide a desired detonation cell size across a plurality of operatingconditions. The various embodiments of the propulsion system providedherein, and methods of operation thereof, include an effervescent fuelatomizing structure that may improve liquid fuel atomization. Theeffervescent fuel atomizing structure may enable larger fuel-oxidizerinjection ports at the rotating detonation combustion system, therebyrelieving the necessity for smaller orifices. The effervescent fuelatomizing structure may further enable control and operating of therotating detonation combustion system at an approximately constantdetonation cell size, thereby enabling operability, combustionstability, and improved performance (e.g. emissions, fuel burn,dynamics, etc.) across a plurality of operating conditions ranging froma lowest pressure and temperature to a highest pressure and temperatureat the rotating detonation combustion system.

Referring now to the figures, FIG. 1 depicts a propulsion system 102including a rotating detonation combustion system 100 (an “RDC system”)in accordance with an exemplary embodiment of the present disclosure.The propulsion system 102 generally includes an inlet section 104 and anoutlet section 106, with the RDC system 100 located downstream of theinlet section 104 and upstream of the exhaust section 106. In variousembodiments, the propulsion system 102 defines a gas turbine engine, aramjet, or other propulsion system including a fuel-oxidizer burnerproducing combustion products that provide propulsive thrust ormechanical energy output. In an embodiment of the propulsion system 102defining a gas turbine engine, the inlet section 104 includes acompressor section defining one or more compressors generating anoverall flow of oxidizer 195 to the RDC system 100. The inlet section104 may generally guide a flow of the oxidizer 195 to the RDC system100. The inlet section 104 may further compress the oxidizer 195 as itenters an inlet 108 of and through the inlet section 104 before itenters the RDC system 100. The inlet section 104 defining a compressorsection may include one or more alternating stages of rotatingcompressor airfoils. In other embodiments, the inlet section 104 maygenerally define a decreasing cross sectional area from an upstream endto a downstream end proximate to the RDC system 100.

As will be discussed in further detail below, at least a portion of theoverall flow of oxidizer 195 is mixed with a liquid fuel 163 (shown inFIG. 2) and detonated to generate combustion products 138. Thecombustion products 138 flow downstream to the exhaust section 106. Invarious embodiments, the exhaust section 106 may generally define anincreasing cross sectional area from an upstream end proximate to theRDC system 100 to a downstream end of the propulsion system 102.Expansion of the combustion products 138 generally provides thrust thatpropels the apparatus to which the propulsion system 102 is attached, orprovides mechanical energy to one or more turbines further coupled to afan section, a generator, or both. Thus, the exhaust section 106 mayfurther define a turbine section of a gas turbine engine including oneor more alternating rows or stages of rotating turbine airfoils. Thecombustion products 138 may flow from the exhaust section 106 through,e.g., an exhaust nozzle 135 to generate thrust for the propulsion system102.

As will be appreciated, in various embodiments of the propulsion system102 defining a gas turbine engine, rotation of the turbine(s) within theexhaust section 106 generated by the combustion products 138 istransferred through one or more shafts or spools to drive thecompressor(s) within the inlet section 104. In various embodiments, theinlet section 104 may further define a fan section, such as for aturbofan engine configuration, such as to propel air across a bypassflowpath outside of the RDC system 100 and exhaust section 106.

It will be appreciated that the propulsion system 102 depictedschematically in FIG. 1 is provided by way of example only. In certainexemplary embodiments, the propulsion system 102 may include anysuitable number of compressors within the inlet section 104, anysuitable number of turbines within the exhaust section 106, and furthermay include any number of shafts or spools appropriate for mechanicallylinking the compressor(s), turbine(s), and/or fans. Similarly, in otherexemplary embodiments, the propulsion system 102 may include anysuitable fan section, with a fan thereof being driven by the exhaustsection 106 in any suitable manner. For example, in certain embodiments,the fan may be directly linked to a turbine within the exhaust section106, or alternatively, may be driven by a turbine within the exhaustsection 106 across a reduction gearbox. Additionally, the fan may be avariable pitch fan, a fixed pitch fan, a ducted fan (i.e., thepropulsion system 102 may include an outer nacelle surrounding the fansection), an un-ducted fan, or may have any other suitableconfiguration.

Moreover, it should also be appreciated that the RDC system 100 mayfurther be incorporated into any other suitable aeronautical propulsionsystem, such as a turboshaft engine, a turboprop engine, a turbojetengine, a ramjet engine, a scramjet engine, etc. Further, in certainembodiments, the RDC system 100 may be incorporated into anon-aeronautical propulsion system, such as a land-based or marine-basedpower generation system. Further still, in certain embodiments, the RDCsystem 100 may be incorporated into any other suitable propulsionsystem, such as a rocket or missile engine. With one or more of thelatter embodiments, the propulsion system may not include a compressorin the inlet section 104 or a turbine in the exhaust section 106.

Referring now to FIGS. 1-2, an exemplary embodiment of an RDC system 100of the propulsion system of FIG. 1 is generally provided. The RDC system100 generally includes a generally cylindrical walled enclosure 119defining, at least in part, a combustion chamber 122, a combustion inlet124, and a combustion outlet 126. The combustion chamber 122 defines anannular combustion chamber length 123 from approximately the combustioninlet 124 to the combustion outlet 126. The combustion chamber 122further defines an annular gap or annular combustion chamber width 121extended from an inner diameter wall to an outer diameter wall. Thecombustion chamber length 123 and the combustion chamber width 121together define a combustion chamber volume. The combustion chamber 122defined by the walled enclosure 119 generally defines a fixed orconstant volume. In the embodiments generally provided herein, thecombustion chamber length 123 and width 121 are each variables fordetermining the volume of the combustion chamber 122. For example, invarious embodiments, the length 123 and width 121 of the combustionchamber 122 is generally sized for a minimum or lowest steady stateoperating condition of the propulsion system, such as a lowest pressureand temperature of oxidizer in the combustion chamber 122. The loweststeady state operating condition of the propulsion system generallyresults in a configuration of the RDC system 100 or, more specifically,the combustion chamber 122, at a maximum volume directly related to adetonation cell size of a fuel-oxidizer mixture in the combustionchamber 122. Still more specifically, the lowest steady state operatingcondition results in a configuration of the combustion chamber 122 at amaximum combustion chamber length 123 and width 121 related to adetonation cell size of fuel-oxidizer mixture in the combustion chamber122.

Referring still to FIGS. 1-2, the RDC system 100 further includes anozzle assembly 128 located at the combustion inlet 124. The nozzleassembly 128 provides a flow mixture of oxidizer and fuel to thecombustion chamber 122, wherein such mixture is combusted/detonated togenerate the combustion products therein, and more specifically adetonation wave 130 as will be explained in greater detail below. Thecombustion products exit through the combustion chamber outlet 126.

The nozzle assembly 128 is defined at the upstream end of the walledenclosure 119 at the combustion chamber inlet 124. The nozzle assembly128 generally defines a nozzle inlet 144, a nozzle outlet 146 adjacentto the combustion inlet 124 and combustion chamber 122, and a throat 152between the nozzle inlet 144 and nozzle outlet 146. A nozzle flowpath148 is defined from the nozzle inlet 144 through the throat 152 and thenozzle outlet 146. The nozzle flowpath 148 defines in part a primaryflowpath 200 through which an oxidizer flows from an upstream end of thepropulsion system through the inlet 108 to the combustion chamber 122and to a downstream end of the propulsion system through the exhaustnozzle 135. The nozzle assembly 128 generally defines aconverging-diverging nozzle, i.e. the nozzle assembly 128 defines adecreasing cross sectional area from approximately the nozzle inlet 144to approximately the throat 152, and further defines an increasing crosssectional area from approximately the throat 152 to approximately thenozzle outlet 146.

Between the nozzle inlet 144 and the nozzle outlet 146, a fuel injectionport 162 is defined in fluid communication with nozzle flowpath 148 or,more generally, the primary flowpath 200, through which the oxidizerflows. The fuel injection port 162 introduces a liquid or gaseous fuel163, or mixtures thereof, to the flow of oxidizer through the nozzleflowpath 148 and, generally, the primary flowpath 200. In variousembodiments, the fuel injection port 162 is disposed at approximatelythe throat 152 of the nozzle assembly 128. In an embodiment of the RDCsystem 100 defining a generally annular walled enclosure 119 (e.g.,defined by an outer wall 118 and an inner wall 120 shown in FIG. 1) anddefining a generally annular combustion chamber 122, a plurality of fuelinjection ports 162 are defined in adjacent circumferential arrangementaround the longitudinal centerline 116.

The primary flowpath 200 extends generally through the propulsion systemfrom the inlet section 104 through the RDC system 100 and the exhaustsection 206. In various embodiments, such as in gas turbine engines, theprimary flowpath 200 extends through the compressor section throughwhich the oxidizer is compressed before entering the RDC system 100.Furthermore, in such an embodiment, the primary flowpath 200 extendsthrough the turbine section through which combustion products expand anddrive one or more turbines that drive one or more compressors, a fansection, or a power generation apparatus. More specifically for the RDCsystem 100 generally provided, the primary flowpath 200 generallyextends through the length of the nozzle flowpath 148 and the combustionchamber 122.

Referring briefly to FIG. 3, providing a perspective view of thecombustion chamber 122 (without the nozzle assembly 128), it will beappreciated that the RDC system 100 generates the detonation wave 130during operation. The detonation wave 130 travels in the circumferentialdirection C of the RDC system 100 consuming an incoming fuel/oxidizermixture 132 and providing a high pressure region 134 within an expansionregion 136 of the combustion. A burned fuel/oxidizer mixture 138 (i.e.,combustion products) exits the combustion chamber 122 and is exhausted.

More particularly, it will be appreciated that the RDC system 100 is ofa detonation-type combustor, deriving energy from the continuous wave130 of detonation. For a detonation combustor, such as the RDC system100 disclosed herein, the combustion of the fuel/oxidizer mixture 132(i.e., the mixture of the fuel 163 and the first portion 205 of oxidizerthrough the primary flowpath 200 as generally provided in FIGS. 1-2) iseffectively a detonation as compared to a burning, as is typical in thetraditional deflagration-type combustors. Accordingly, a main differencebetween deflagration and detonation is linked to the mechanism of flamepropagation. In deflagration, the flame propagation is a function of theheat transfer from a reactive zone to the fresh mixture, generallythrough conduction. By contrast, with a detonation combustor, thedetonation is a shock induced flame, which results in the coupling of areaction zone and a shockwave. The shockwave compresses and heats thefresh mixture 132, increasing such mixture 132 above a self-ignitionpoint. On the other side, energy released by the combustion contributesto the propagation of the detonation shockwave 130. Further, withcontinuous detonation, the detonation wave 130 propagates around thecombustion chamber 122 in a continuous manner, operating at a relativelyhigh frequency. Additionally, the detonation wave 130 may be such thatan average pressure inside the combustion chamber 122 is higher than anaverage pressure within typical combustion systems (i.e., deflagrationcombustion systems). Accordingly, the region 134 behind the detonationwave 130 has very high pressures.

Referring now to FIGS. 1-3, the propulsion system 102 generally includesan effervescent fuel atomizing structure 165 (hereinafter “effervescentatomizer 165”) configured to provide an effervescent flow of a mixture163 of gas 159 and liquid fuel 161 through the nozzle assembly 128 ofthe RDC system 100 and into the primary flowpath 200 for detonation intocombustion products 138. In one embodiment, such as generally providedin FIG. 1, the gas 159 is an oxidizer, such as air, or an inert gas, ora gaseous fuel. In another embodiment, such as generally provided inFIG. 2, the gas 159 is at least a portion of the oxidizer 195, such asair, drawn from the primary flowpath 200. The effervescent atomizer 165may improve rapid mixing of the liquid fuel 161 when it is injected intothe primary flowpath 200 and further mixed with the oxidizer 195. Theeffervescent atomizer 165 may further enable larger fuel injection ports162 at the nozzle assembly 128, thereby reducing a need for small ortight-tolerance openings that may impede application of RDC systems 100into smaller applications (e.g., ramjets, scramjets, missiles, rockets,etc.).

For example, a fuel injection port configured solely to flow a liquidfuel may define a diameter D. However, the fuel injection port 162configured to flow the mixture 163 of gas 159 and liquid fuel 161defines a diameter at least approximately 50% greater (1.5×) thandiameter D. In various embodiments, the fuel injection port 162 maydefine a diameter at least approximately double (2×) of the diameter D,in which diameter D defines solely a liquid fuel flow to the nozzleflowpath 148. In such an embodiment, the fuel injection port 162 mayflow the mixture 163 of gas 159, defining a gaseous fuel such as, butnot limited to, hydrogen, and liquid fuel 161. As such, the larger fuelinjection ports 162 may reduce the need for small or tight-tolerancefuel injection ports to the nozzle flowpath of the RDC system. Thelarger fuel injection ports 162 may further mitigate risk of clogging orother flow restriction due to impurities (e.g., dirt, fuel coking,carbon, etc.), domestic object debris (DOD), or foreign object debris(FOD) that may reduce combustion operation, efficiency, or performance.

The effervescent atomizer 165 generally includes a flow of gas 159 and aflow of liquid fuel 161 through separate conduits, manifolds, or otherwalled structures. A valve 167 regulates a ratio of mixture 163 of gas159 and liquid fuel 161 into an effervescent flow manifold 168 leadingto the nozzle assembly 128 and the primary flowpath 200. Theeffervescent atomizer 165 may further include one or more pressure,temperature, and/or flow sensors to monitor, measure, or calculate theflow of gas 159, liquid fuel 161, or the mixture 163, to the nozzleassembly 128 and primary flowpath 200. The one or more sensors mayfurther provide data used to calculate a volumetric flow, or ratiothereof, of the gas 159 versus liquid fuel 161 in the mixture 163. Thecalculated volumetric flow may be utilized by the valve 167 to adjust aratio of the gas 159 versus the liquid fuel 161 in the mixture 163 basedat least on one or more operating conditions of the propulsion system102, such as further explained in regard to FIGS. 7-8 providingflowcharts outlining exemplary steps of operating the propulsion system102.

Although shown as a valve 167, the effervescent atomizer 165 may includea plurality of regulators or valves 167 (e.g., one-way valves, checkvalves, pressure regulating valves, etc.) that may combine the gas 159and the liquid fuel 161 at a desired pressure, flow, or both. Forexample, the valve 167, or a plurality thereof, may be utilized tocombine the gas 159 and the liquid fuel 161 at approximately equalpressures.

The effervescent atomizer 165 may further include one or more pumps toincrease a pressure of the gas 159, the liquid fuel 161, or both to thenozzle assembly 128. In one embodiment, in which the RDC system 100defines a combustion section of a propulsion system, the pumps mayprovide the pressure necessary to overcome the pressure at the primaryflowpath 200. However, in other embodiments, such as the RDC system 100defining an inter-turbine burner or an afterburner to a propulsionsystem, the pumps may be excluded from the effervescent atomizer 165.

Though not provided in further detail, the propulsion system 102generally provided in FIGS. 1-6 further includes a computing device thatincludes one or more processors and one or more memory devices. The oneor more memory devices stores instructions that when executed by the oneor more processors cause the one or more processors to performoperations. The operations include one or more of the steps generallyprovided in FIGS. 7-8 of the flowcharts outlining exemplary steps of amethod of effervescent atomization of a liquid fuel (e.g., liquid fuel161) with a gas (e.g., gas 159) in a propulsion system (e.g., propulsionsystem 102). The computing device is further configured to execute oneor more operations for operating a propulsion system at an approximatelyconstant detonation cell size at the combustion chamber (e.g.,combustion chamber 122) of an RDC system (e.g. RDC system 100).

The technology discussed herein makes reference to computer-basedsystems and actions taken by and information sent to and fromcomputer-based systems. One of ordinary skill in the art will recognizethat the inherent flexibility of computer-based systems allows for agreat variety of possible configurations, combinations, and divisions oftasks and functionality between and among components. For instance,processes discussed herein can be implemented using a single computingdevice or multiple computing devices working in combination. Databases,memory, instructions, and applications can be implemented on a singlesystem or distributed across multiple systems. Distributed componentscan operate sequentially or in parallel. In various embodiments, thecomputer-based systems may include one or more of, or a combination of,a full authority digital engine controller (FADEC), an electronic enginecontroller (EEC), an engine control unit (ECU), a power module, one ormore sensors, actuators, transducers, or combinations thereof that maymonitor, control, adjust, or otherwise manipulate a fluid flow withinthe propulsion system 102, including, but not limited to, the flow,pressure, and/or temperature of the oxidizer 195, gas 159, liquid fuel161, and the gas-liquid fuel mixture 163.

Referring now to FIG. 7, a flowchart outlining exemplary steps of amethod of effervescent atomization of liquid fuel for a rotatingdetonation combustor (RDC) for a propulsion system is generally provided(herein after “method 700”). The method 700 generally provided in FIG. 7may be implemented with various embodiments of a propulsion system andRDC system, such as the propulsion system 102 and RDC system 100 shownand described in regard to FIGS. 1-7. The method 700 may improve liquidfuel atomization into a primary flowpath to be mixed and detonated withan oxidizer with improved efficiency, specific fuel consumption, andemissions. The method 700 may provide one or more of the aforementionedbenefits while further enabling enlarged fuel injection ports (e.g., thefuel injection ports 162), thereby enabling application of RDC systemsinto apparatuses in which extremely small fuel injection ports may limitapplication of the RDC system.

The method 700 may be implemented with a propulsion system and RDC suchas those described in regard to FIG. 1-5. FIG. 7 depicts steps performedin a particular order for purposes of illustration and discussion. Thoseof ordinary skill in the art, using the disclosures provided herein,will understand that the various steps of any of the methods disclosedherein can be modified, adapted, expanded, rearranged and/or omitted invarious ways without deviating from the scope of the present disclosure.

The RDC system may generally include a nozzle assembly configured toadmit a flow of liquid fuel and a gas for mixing before injecting thegas-liquid fuel mixture to a primary flowpath through which an oxidizerflows. The method 700 includes at 710 flowing liquid fuel through a fuelinjection port of a nozzle assembly of the RDC system; at 720 flowing agas through the fuel injection port of the nozzle assemblyvolumetrically proportional to the liquid fuel; at 730 producing agas-liquid fuel mixture at the fuel injection port by mixing the flow ofgas and the flow of liquid fuel; at 740 flowing an oxidizer through anozzle flowpath of the RDC system; at 750 producing anoxidizer-gas-liquid fuel mixture by mixing the gas-liquid fuel mixtureand the flow of oxidizer within the nozzle flowpath; and at 760 ignitingthe oxidizer-gas-liquid fuel mixture within a combustion chamber of theRDC system.

In various embodiments, the liquid fuel includes, but is not limited to,a diesel, kerosene, naphtha, ethanol, methanol, oil, liquefied naturalgas, liquefied petroleum gas, or combinations thereof. Variousembodiments of the liquid fuel may be referred to as Jet A, Jet A−1, JetB, or one or more Jet Propellant (JP) fuels.

In still various embodiments, the gas may include air, an inert gas, agaseous fuel, or combinations thereof. The gaseous fuel may includehydrogen, coal gas, coke oven gas, refinery gas, ethane gases, includingethylene, or combinations thereof.

In one embodiment at 710, flowing a liquid fuel through a fuel injectionport of a nozzle assembly includes flowing the liquid fuel 161 throughthe fuel injection port 162 of the nozzle assembly 128 generallyprovided in FIGS. 1-7. In various embodiments, the flow is provided,maintained, monitored, calculated, or controlled based at least on avolumetric flow rate of the liquid fuel.

In various embodiments at 730, producing a gas-liquid fuel mixtureincludes producing a volumetric flow ratio of gas to liquid fuel ofapproximately 1000% or less. For example, the volumetric flow of gasversus liquid fuel may be approximately 10 to 1 or less. In anotherembodiment at 720, producing a gas-liquid fuel mixture includesproducing a mass flow ratio of gas to liquid fuel of approximately 30%or less.

Referring briefly to FIG. 6, a two-phase chart 600 is generally providedshowing a relationship of gas volumetric flux and liquid volumetricflux. In various embodiments, the volumetric flow of gas versus liquidfuel may be at least sufficient to induce a disperse flow (such asgenerally shown in FIG. 5) of the gas-liquid fuel mixture 163, or anannular or annular/mist flow of the gas-liquid mixture 163 (such asgenerally shown in FIG. 4).

Referring back to FIG. 7, in various embodiments of the method 700 at720, flowing a gas includes flowing a gaseous fuel. In one embodiment,flowing the gaseous fuel includes flowing a gaseous fuel defining adetonation cell size of the gaseous fuel less than a detonation cellsize of the liquid fuel. In one non-limiting example, the gaseous fueldefines hydrogen or an ethane gas, such as ethylene, defining adetonation cell size less than the liquid fuel defining, for example, akerosene-based fuel such as Jet A.

Referring now to FIG. 8, a flowchart outlining exemplary steps of amethod of operating a propulsion system at an approximately constantdetonation cell size for a propulsion system comprising a rotatingdetonation combustion (RDC) system (hereinafter “method 800”) isgenerally provided. The method 800 may be implemented usingsubstantially similar systems, apparatuses, etc. as described in regardto FIGS. 1-8. Furthermore, the method 800 generally incorporates thesteps described in regard to the method 700 outlined in regard to FIG.7.

It should be appreciated that the method 800 may be implemented with apropulsion system and RDC such as those described in regard to FIGS.1-7. FIG. 8 depicts steps performed in a particular order for purposesof illustration and discussion. Those of ordinary skill in the art,using the disclosures provided herein, will understand that the varioussteps of any of the methods disclosed herein can be modified, adapted,expanded, rearranged and/or omitted in various ways without deviatingfrom the scope of the present disclosure.

The method 800 includes at 810 flowing a liquid fuel through a fuelinjection port of a nozzle assembly of the RDC system; at 820 flowing agaseous fuel through the fuel injection port of the nozzle assemblyvolumetrically proportional to the liquid fuel; at 830 producing agas-liquid fuel mixture at the fuel injection port by mixing the flow ofgas and the flow of liquid fuel; at 840 flowing an oxidizer through anozzle flowpath of the RDC system; at 850 producing anoxidizer-gas-liquid fuel mixture by mixing the gas-liquid fuel mixtureand the flow of oxidizer within the nozzle flowpath; at 860 igniting theoxidizer-gas-liquid fuel mixture within a combustion chamber of the RDCsystem; and at 870 adjusting a volumetric flow of gaseous fuel relativeto the liquid fuel based at least on a commanded operating condition ofthe propulsion system.

The steps at 810 through 860 may include the descriptions, embodiments,one or more limitations, or combinations thereof described in regard tosteps 710 through 760 of method 700.

In various embodiments of the method 800, at 820 flowing a gaseous fuelis based at least on a desired detonation cell size at a first operatingcondition of the propulsion system. The first operating condition maygenerally refer to a lowest steady state pressure and/or temperature atthe RDC system following initial ignition or start-up of the propulsionsystem. For example, in an embodiment in which the propulsion systemdefines a gas turbine engine, the first operating condition may beground idle. At the first operating condition, the RDC system defines aminimum quantity of detonation cells and approximately constant cellsize suitable for stable or optimal operation of the RDC system. The RDCsystem, such as the combustion chamber 122, may define the annular gap121, the combustion chamber length 123, or both to produce a desiredquantity and size of detonation cells at the pressure and temperatureconditions of the oxidizer and the flow of gas-liquid fuel mixturecorresponding to the first operating condition.

The propulsion system further defines a second operating conditiondifferent from the first operating condition. The second operatingcondition generally defines pressures and temperatures at the RDC systemgreater than the first operating condition. For example, in anembodiment in which the propulsion system defines a gas turbine engine,the second operating condition may define one or more steady stateconditions such as maximum takeoff, climb, cruise, flight idle,approach, reverse thrust, etc., and transient conditions therebetween.

In one embodiment at 870, adjusting the volumetric flow of gaseous fuelis based at least on maintaining an approximately constant detonationcell width at a second operating condition greater than the firstoperating condition. In various embodiments, the volumetric flow ofgaseous fuel mixed with the liquid fuel is based at least in part onmaintaining an approximately constant detonation cell size at the secondoperating condition (i.e., the plurality of operating conditions of thepropulsion system greater than the first operating condition) relativeto the first operating condition defining a lowest steady stateoperating condition.

In another embodiment at 870, adjusting the volumetric flow of gaseousfuel is based at least on maintaining an approximately constantdetonation cell size at a stoichiometric ratio of detonated fuel andoxidizer of approximately 1.0 or less at the second operating condition.In still other embodiments at 870, adjusting the volumetric flow ofgaseous fuel is based at least on a pressure and a temperature ofoxidizer at the RDC system.

For example, the combustion chamber 122 of the RDC system 100 may beconfigured to yield a stoichiometric ratio of detonated fuel andoxidizer 138 of approximately 1.0 or less at the first operatingcondition. The detonation cell size of the detonated fuel-oxidizermixture 138 may be based on the annular gap 121 and the combustionchamber length 123 together defining a generally fixed or constantvolume of the combustion chamber 122. The volume may be based at leaston maintaining a desired operation or performance of the propulsionsystem 102 at a lowest steady state operating condition followingignition or light off. As the propulsion system 102 changes from thefirst operating condition to the second operating condition, thedetonation cell size may generally change as a function of at least thepressure and temperature of oxidizer 195 entering the RDC system 100 andthe gas-liquid fuel mixture 163 mixing with the oxidizer 195.

More specifically, in various embodiments, flowing the gaseous fuelincludes flowing a gaseous fuel defining a detonation cell width of thegaseous fuel less than a detonation cell width of the liquid fuel. Forexample, the detonation cell size is at least a function of the cellsize properties of the liquid fuel 159 and the gaseous fuel 161 and theratio each fuel 159, 161 in the gas-liquid fuel mixture 163. Forexample, the liquid fuel 159 (e.g., Jet A) may generally define a largerdetonation cell size than the gaseous fuel (e.g., hydrogen, ethylene).Adjusting the ratio of the gaseous fuel 161 mixed with the liquid fuel159 may adjust the detonation cell size of the gas-liquid fuel mixture163. Adjusting the ratio of the gaseous fuel 161 mixed with the liquidfuel 159 relative to the pressure and temperature of oxidizer 195entering the RDC system 100 (and changes thereof relative to theplurality of second operating condition of the propulsion system 102)may maintain an approximately constant detonation cell size at thecombustion chamber 122 from the first operating condition to theplurality of second operating conditions.

The methods 700 and 800 may further include at 780 and 880,respectively, adjusting the flow of liquid fuel based at least on thecommanded operating condition of the propulsion system. The commandedoperating condition of the propulsion system (e.g., propulsion system102) may generally include any user input or computer input desiredoperating condition. In various embodiments, such as a propulsion systemproviding thrust or other locomotive force for an aircraft, thecommanded operating condition may be based on a power level angle orthrust lever position. One or more computing devices including one ormore processors and one or more memory devices configured to storeinstructions and execute operations may translate the commandedoperating condition into one or more parameters based at least on one ormore of a commanded thrust output, shaft speed, and engine pressureratio (EPR). For example, the commanded thrust output, the shaft speed(e.g., fan shaft speed N_(FAN), propeller speed, low spool speed N₁ orN_(L), intermediate spool speed N₁, high spool speed N₂ or N_(H), etc.),and the EPR may be based at on one or more parameters such as a fuelflow rate and/or pressure, and oxidizer flow rate, pressure, and/ortemperature, one or more variable guide vane or variable stator vaneangles, one or more bleed valve positions (e.g., percentage open orclose), or combinations thereof that may output an actual thrust output,shaft speed, or EPR based on the commanded operating condition.

The methods 700 and 800 generally provided herein may further define theratio of gas and liquid fuel mixture of the fuel flow that may producethe actual thrust output, shaft speed, or EPR based on the commandedoperating condition. For example, the methods 700 and 800 may generallydetermine a volumetric flow rate of gas to mix with the liquid fuelbased at least on the liquid fuel flow rate and a desired two-phase flowregime of a gas-liquid fuel mixture such as generally provided in FIG.7. The mixture of gas and liquid fuel may provide an effervescentatomization of the fuel mixture 163 that may yield combustion products138 with desired or optimal levels of emissions, specific fuelconsumption, and operability, such as a desired detonation cell sizeacross a plurality of operating conditions.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A propulsion system, the propulsion system comprising: a rotating detonation combustion (RDC) system, the RDC system comprising a combustion chamber and a fuel injection port, the fuel injection port configured to receive a flow of a liquid fuel therethrough and provide the flow of the liquid fuel to a nozzle flowpath; an inlet section including a compressor configured to flow an oxidizer through the RDC system; a valve configured to control the flow of the liquid fuel and a flow of a first portion of the oxidizer; a first pump configured to flow the liquid fuel through the fuel injection port; an ignition device; and a computing device configured to perform operations, the operations comprising; controlling the compressor to flow the first portion of the oxidizer through the fuel injection port and a second portion of the oxidizer through the nozzle flowpath; controlling the first pump to flow the liquid fuel through the fuel injection port; controlling the valve to produce a first mixture at the fuel injection port by mixing the flow of the first portion of the oxidizer and the flow of the liquid fuel, wherein a second mixture is formed as the first mixture is injected from the fuel injection port into the flow of the second portion of the oxidizer within the nozzle flowpath; controlling the ignition device to ignite the second mixture at the combustion chamber; and adjusting the valve to adjust a volumetric flow rate of the first portion of the oxidizer relative to a volumetric flow rate of the liquid fuel based at least on a commanded operating condition of the propulsion system.
 2. The propulsion system of claim 1, wherein a volumetric flow ratio of the volumetric flow rate of the first portion of the oxidizer to the volumetric flow rate of the liquid fuel is 1000% or less.
 3. The propulsion system of claim 1, wherein a pressure of the first portion of the oxidizer is greater than a pressure of the flow of the liquid fuel within the fuel injection port.
 4. The propulsion system of claim 1, wherein a mass flow ratio of the first portion of the oxidizer to the liquid fuel is 30% or less.
 5. The propulsion system of claim 1, wherein the first mixture defines an annular flow, a mist flow, or a disperse flow of first mixture based at least on a volumetric flux of the first portion of the oxidizer and a volumetric flux of the liquid fuel.
 6. The propulsion system of claim 1, the propulsion system comprising: a second pump configured to pressurize the first portion of the oxidizer.
 7. The propulsion system of claim 1, wherein the commanded operating condition is indicated by one or more parameters comprising a commanded thrust output, a shaft speed, an engine pressure ratio, the volumetric flow rate of the liquid fuel, a pressure of the first portion of the oxidizer, a pressure of the second portion of the oxidizer, a temperature of the first portion of the oxidizer, or a temperature of the second portion of the oxidizer; and the operations further comprising: determining the volumetric flow rate of the first portion of the oxidizer to mix with the liquid fuel based at least on the volumetric flow rate of the liquid fuel and a desired two-phase flow regime of a gas-liquid fuel mixture.
 8. The propulsion system of claim 7, wherein adjusting the valve maintains a desired detonation cell width the combustion chamber.
 9. The propulsion system of claim 8, wherein the desired detonation cell width is based at least on a pressure of the first portion of the oxidizer, a pressure of the second portion of the oxidizer, a temperature of the first portion of the oxidizer, a temperature of the second portion of the oxidizer, a volumetric flow ratio of the first mixture, an annular gap of the combustion chamber, and a combustion chamber length.
 10. A rotating detonation combustion (RDC) system, the RDC system comprising: a combustion chamber and a fuel injection port, the fuel injection port configured to receive a flow of a liquid fuel therethrough and provide the flow of the liquid fuel to a nozzle flowpath; a valve configured to control the flow of the liquid fuel and a flow of an inert gas; a first pump configured to flow the liquid fuel through the fuel injection port; a second pump configured to flow the inert gas through the fuel injection port; and a computing device configured to perform operations, the operations comprising; controlling the first pump to flow the liquid fuel through the fuel injection port; controlling the second pump to flow the inert gas through the fuel injection port; controlling a compressor to flow an oxidizer through the nozzle flowpath; controlling the valve to produce a first mixture at the fuel injection port by mixing the flow of the inert gas and the flow of the liquid fuel, wherein a second mixture is formed as the first mixture is injected from the fuel injection port into the flow of the oxidizer within the nozzle flowpath; controlling an ignition device to ignite the second mixture at the combustion chamber of the RDC system; and adjusting the valve to adjust a volumetric flow rate of the inert gas relative to a volumetric flow rate of the liquid fuel based at least on a commanded operating condition.
 11. The RDC system of claim 10, wherein a volumetric flow ratio of the volumetric flow rate of the inert gas to the volumetric flow rate of the liquid fuel is 1000% or less.
 12. The RDC system of claim 10, wherein a mass flow ratio of the inert gas to the liquid fuel is 30% or less.
 13. A rotating detonation combustion (RDC) system, the RDC system comprising: a combustion chamber and a nozzle assembly, the nozzle assembly comprising a fuel injection port and a nozzle flowpath, the fuel injection port configured to receive a flow of a liquid fuel therethrough and provide the flow of the liquid fuel to the nozzle flowpath; a valve configured to control a flow of the liquid fuel and a flow of a gaseous fuel; a first pump configured to flow the liquid fuel through the fuel injection port; a second pump configured to flow the gaseous fuel through the fuel injection port; and a computing device configured to perform operations, the operations comprising; controlling the first pump to flow the liquid fuel through the fuel injection port; controlling the second pump to flow the gaseous fuel through the fuel injection port; controlling a compressor to flow an oxidizer through the nozzle flowpath; controlling the valve to produce a first mixture at the fuel injection port by mixing the flow of the gaseous fuel and the flow of the liquid fuel, wherein a second mixture is formed as the first mixture is injected from the fuel injection port into the flow of the oxidizer within the nozzle flowpath; controlling an ignition device to ignite the second mixture within the combustion chamber; and adjusting the valve to adjust a volumetric flow rate of the gaseous fuel relative to a volumetric flow rate of the liquid fuel based at least on a commanded operating condition.
 14. The RDC system of claim 13, the operations comprising: adjusting the first pump to adjust the flow of the liquid fuel based at least on the commanded operating condition.
 15. The RDC system of claim 13, wherein adjusting the valve maintains a desired detonation cell width at a second operating condition, the second operating condition at greater pressures or temperatures than a first operating condition.
 16. The RDC system of claim 15, wherein the constant detonation cell width is maintained at a stoichiometric ratio of 1.0 or less at the second operating condition.
 17. The RDC system of claim 13, wherein a detonation cell width of the gaseous fuel less is than a detonation cell width of the liquid fuel.
 18. The RDC system of claim 13, the operations comprising: determining a gaseous fuel volumetric flux; determining a liquid fuel volumetric flux; and wherein the first mixture defines an annular flow, a mist flow, or a disperse flow based at least on the gaseous fuel volumetric flux and the liquid fuel volumetric flux. 